Whole blood samples are often fractionated to separate red blood cells, platelets, and other cellular materials from the plasma and other fluid components of the whole blood. A selected fraction, typically red blood cells or cellular materials, can be selectively withdrawn from the fractionated whole blood sample for use in certain medical applications. The isolated cellular material is often further processed by adding one or more wash fluids to the isolated cellular materials to remove any plasma or other undesirable fluids or materials clinging to or intermixed with the desired cellular material. The resulting wash fluid comprising cellular material within the wash fluids is often fractionated again to separate and isolate the cellular material from the wash fluids.
For certain medical applications, the cellular materials must often be washed multiple times to cleanse the cellular material to certain predetermined standards. During centrifugation, the cellular material compresses into a bed or pack of cells. Repeated washing can disrupt the cell pack dislodging cellular material, which can become entrained within the wash fluid and discarded with the wash fluid after each wash cycle. However, as the cellular materials are only loosely packed together and not substantially adhered to each other, adding any wash fluid to the cell pack can easily dislodge cells from the cell pack resulting in unnecessary waste.